Solution:
Let the number of large boxes be

Let the number of small boxes be

The total number of boxes are

The system of equation to represent this will be given below as

The large box weigh

The small box weigh

The total weight of the boxes is

The system of the equation to represent this is

Step 1:
From equation (1) make x the subject of the formula to form equation (3)

Step 2:
substitute equation (3) in equation (2)

Substitute the value of y=50 in equation (3)

Hence,
Number of large boxes = 65
Number of small boxes = 50